1. Field of the Invention
The present invention relates to an optical disc recording apparatus, an optical disc reproducing apparatus, an optical disc recording and reproducing apparatus, and an optical disc. Especially, the present invention relates to a recording apparatus, a reproducing apparatus, a recording and reproducing apparatus and an optical disc of ZCAV (Zoned Constant Angular Velocity) system.
2. Description of the Related Art
There are a CAV (Constant Angular Velocity) system, a CLV (Constant Linear Velocity) system, etc. as a recording and reproducing system of digital data of an optical disc.
In the CAV system, the access speed is high, since the number of rotations of the optical disc, i.e., the angular velocity, is constant. Therefore, the line velocity becomes low at the inner circumferential side of the optical disc, and becomes high at the outer circumferential side. For this reason, the recording density of the outer circumferential side becomes low. The recording time comes to be proportional to the diameter of the optical disc.
In the CLV system, the line velocity becomes constant. This is because the number of rotations of the optical disc is great at the inner circumferential side and is little at the outer circumferential side. Therefore, the recording time is proportional to the area of the optical disc. The data rate is fixed or constant irrespective of the recording position. As the result, it becomes possible to perform record and reproduction of data of high density.
Here, the outline of recording and reproducing operation of the recording and reproducing apparatus of CLV system optical disc (hereinbelow, it is called as "CLV disc"), will be explained.
The recording and reproducing apparatus extracts a reproduction clock signal from the reproduction signal of the CLV disc at the time of information reproduction of the CLV disc. The recording and reproducing apparatus applies a servo-control to a spindle motor so that this reproduction clock signal may become to have a fixed frequency. As the result, the reproduction data rate of the record data on the CLV disc becomes fixed. On the other hand, at the time of information recording, the recording and reproducing apparatus reads the CLV disc by an optical pickup. A pregroove and a prepit are formed on the record track position of the CLV disc beforehand. The recording and reproducing apparatus rotationally drives the CLV disc so that the reproduction clock of the reproduction signal may become constant. The recording and reproducing apparatus records data inputted at a fixed data rate.
On the other hand, there are a ZCAV system and a MCAV (Modified Constant Angular Velocity) system, which realize a high density record and reproduction, by fixing the number of rotations of the optical disc.
This ZCAV system divides the record area of the optical disc into two or more zones. The ZCAV system rotationally drives the optical disc by a constant angular velocity. The ZCAV system sets constant the data rate of record and reproduction in the same zone, and sets higher the data rate of record and reproduction in the outer zone than that in the inner zone. Therefore, the ZCAV system can record and reproduce more data per one track than the CAV system.
In the CAV system, since the angular velocity is constant, the access speed is high. However, there is a problem that a recording density becomes low. On the other hand, in the CLV system, the recording density is high. However, in order to make the line velocity,constant, there is the necessity of changing the number of rotations of the optical disc in accordance with the radius of a reading position. For this reason, it takes time for the rotation to be stabilized, and thus, there is a problem that the access speed becomes low. Furthermore, the data rate changes for every record zone in the ZCAV system. Therefore, there is a problem that it cannot be used in recording and reproducing a signal which requires a constant data rate such as an image data and a sound data.